Level Tomes, what to do with them?
If you have a free character slot you could use them to do Black Lion Key runs: make a new character, get to level 10, complete the story, get a key, delete and repeat next week when the allowance resets.
If you like/don’t mind the story and don’t mind spending more time on it you can level them to 40 for an additional key (and 60 for a 3rd one, but I find that takes too long).
Otherwise if you really don’t need them and they’re taking up too much space you could always just delete them. Although I recommend keeping at least 80 just in case – it may be unlikely but it means if you ever want an instant level 80 you’ve got the option.
“Life’s a journey, not a destination.”
I’m saving them for… well, I can afford the space. I do use them for key runs (I have tried to use up spirit shards faster than I acquire them, but this has proven impossible, so I don’t bother anymore).
One thing that’s nice is that recently, I’ve twice boosted a character to 80 only to realize I made a tragic mistake in character creation (bad look or color or something… or decided against a second of the same prof). Having “too many” tomes meant that it was no big deal to re-roll; all it cost me was a few minutes of time.
Another option is to create an L80 and claim all the leveling rewards; repeat until bored. It’s not a particularly fun or efficient use, but you do get some things that aren’t easily available otherwise: a wxp booster, karma booster, etc.